1. Field of the Invention
The present invention relates to hip replacement systems; and, more particularly, to a femoral hip stem explant system for the removal of remnant cement mantle following the removal of a femoral prosthesis.
2. Description of the Prior Art
Many patents address issues related to removal of a cement mantle incorporated in the bone cavity, typically used to attach a femoral implant. The femoral implant must be extracted and replaced with a new implant when the implant sockets have worn out or due to poor bond formation. The prosthesis is easily extracted by the application of pressure, but the bone cement mantle used during the implant procedure remains attached to the bone cavity and must be removed by drilling, dissolution or other means. Most commonly used methods include free hand drilling wherein the surgeon uses a drill to approximate the location of the bone cement mantle and significant damage may occur to the bone canal including bone fracture which precludes the possibility of a new implant. In some cases the surgeons use an x-ray fluoroscope to get an outline of the bone cavity and the drill, to manually guide the drill within the bone cavity when drilling out bone cement mantle. Drilling of a hardened bone cement mantle can result in heat generation that may damage bone tissue adjacent to the mantle. This damage may prevent bond formation between the femoral bone and the newly implanted femoral implant. It is therefore necessary to limit the amount of heat generated during this bone cement mantle removal procedure. Methods of bone cement mantle removal disclosed in prior art patents generally comprise (i) sawing, to cuts along the side of the mantle; grinding, using a tracing grinding element, the path of which tracks a template; (iii) casting, to cast a resin inside the bone cavity; and (iv) pulling on the resin, to forcefully remove the bone cement mantle. In lieu of pulling on the resin, there is used a fixture that is attached to the femoral bone by interference. This fixture carries a drill that is translated to drill out the bone cement mantle.
U.S. Pat. No. 4,476,861 to Dimakos et al. discloses an instrument for removal of a hollow bone cement tube from an artificial femur head reimplantation. This instrument has an elongate hollow tube adapted to be inserted into the bone cement tube. The end of the hollow tube within the bone canal has a collet comprising a slot. The slot is expanded by a central mandrel rod so that the collect engages the end of the bone cement tube. A cylindrical striker sliding on the hollow tube applies pressure to the bone cement tube enabling its extraction. For this device to work, a free end that is essentially flat must be available within the bone cement tube so that the collet may be engaged for extraction. This feature is oftentimes unavailable. Moreover, a large amount of force must be applied to release and displace the bone cement tube, which may not be available by the simple back and forth movement of the cylindrical striker.
U.S. Pat. No. 4,702,236 to Tarabichy et al. discloses a revision arthroplasty method and related instrument. This method is for revision arthroplasty or the removal of a loosened or defective prosthesis component set in a bone cavity using polymer cement. The loosened or defective prosthesis is then removed out of the bone cavity. Cement is then removed from the cavity by the use of an instrument having a heated working end. Heating the working end to a temperature exceeding the melting point of the cement enables cement to be removed without perforating or damaging the bone. Such heat in the range of 150° C.-200° C. provides an invasive procedure, and can be damaging to bone tissue, preventing bond formation of an implanted prosthesis.
U.S. Pat. Nos. 4,846,161 and 4,986,826 to Roger disclose a method and apparatus for removing prosthetic cement. This method and device is for use in removing the prosthetic cement from a bone in which an artificial joint, such as hip joint, is to be replaced. The device cuts the prosthetic cement in a longitudinal plane of the prosthetic cavity to the complete depth of the cement, without substantially cutting into the bone. The device includes a reciprocating saw head, which is advanced longitudinally of the cavity and is maintained within the preselected longitudinal plane of the cavity by a guide while it cuts through the cement. The saw head is transversly biased towards the cement, so that it cuts only to a depth defined by the profile of a template. The profile of the template is obtained from X-ray information obtained before commencement of the operation. This reciprocating cutting action only produces a cut in the longitudinal plane of the prosthetic cement. Such a cut does not guarantee easy removal of the prosthetic cement, since the cement is shown to be three dimensional in structure matching the shape of the template. Cutting debris is left behind within the bone cavity, and excessive heating is generated by the cutting action, damaging bone tissue. Multiple cuts are needed to effect any removal of the prosthetic cement. The bottom plug of the prosthetic cement is said to be removed by this removal procedure. However, the saw does not reach the very bottom of the cavity. Consequently, these multiple sections are still held together by the bottom uncut portion, making the removal of the prosthetic cement difficult.
U.S. Pat. No. 4,860,735 to Davey et al. discloses a drill alignment guide for osteoplastic surgery. This drill alignment apparatus for osteoplastic surgery comprises an alignment rod mounted on one or two spaced clamp elements. The alignment rod is parallel to and is disposed at a predetermined distance from a shaft of the drill. The clamp element includes an aperture, which permits passage of the rod. The clamp element is adapted to be affixed to a bone, such as a femur, by interference. With this arrangement, the aperture is displaced from the central axis of the bone by substantially the same distance that the center axis of the alignment rod is displaced from the center axis of the drill shaft. When drilling is commenced, the forward end of the alignment rod is placed within the aperture of the clamp element. As drilling progresses, the rod passes through the aperture, thereby ensuring that drilling occurs along a predetermined drilling path extending along the bone axis. The clamping elements merely rest on the femoral bone with no bottom support. Accordingly, they are subject to lifting, especially when a drilling load is applied. When two clamping elements are used, the parallelism of the alignment rod with respect to the bone cavity is not possible, since the shape of the femoral bone is not exactly cylindrical. An alignment rod support is used to attach the drill to the alignment rod. Thus supported, the alignment rod progressively passes through the aperture in one or two clamp elements as the drill enters through the intramedullary bone canal. However, vertical displacement of the clamp element without any bottom support can cause drilling in a path that is not concentric with the intramedullary bone canal.
U.S. Pat. No. 4,919,153 to Chin discloses a method and apparatus for removing pre-placed prosthetic joints and preparing for their replacement. This method and apparatus removes a pre-placed prosthetic joint from a bone cavity and conditions the cavity for receipt of a replacement joint. The pre-placed joint is first pulled from the mantle of hardened methylmethacrylate cement holding it within the cavity, thus leaving a cavity within the mantle. A mass of fluid methylmethacrylate cement is then placed within the cement cavity. A pulling appliance is inserted into the fluid cement and the fluid cement is permitted to cure to bond the appliance to the mantle. Tension is then applied to the pulling appliance to remove the appliance and the cement mantle from the bone cavity as a unit. The fluid cement partially dissolves and softens the hardened cement mantle so that an integral cement mass is formed upon curing of the fluid cement. The pulling appliance is of a screw-like configuration, with means to connect a slap-hammer to its proximal end. The curing of the fluid methylmethacrylate occurs by exothermic reaction of liquid methyl methacrylate monomer with a finely divided powder mixture of polymethyl methacrylate, methyl methacrylate-styrene-copolymer. This exothermic reaction results in large heat generation, damaging bone tissue and resulting in poor bonding of the new implant. The removal of the bone cement mantle within the cavity by this pulling method requires the cavity to be uniformly tapered outward with the progressively larger dimension towards the bone canal opening. This may not be the case in all intramedullary bone canals since the femoral implant is forced into the canal with the bone cement.
U.S. Pat. No. 5,041,120 to McColl et al. discloses a multipart kit and method of using the same to remove cement used to secure prosthetic joints. A mantle of cement within a bone elongate cavity is removed from the adhered condition by successively breaking away sections of the mantle with a plurality of elongate screw threaded pulling elements proportioned to engage a limited length of a screw threaded mass of cement within the cavity. The apparatus is provided in a kit form having a sufficient number of elements to enable the full length of the mantle to be removed in successive steps. The kit may also include a cement injection syringe and vent tube to fill the cavity of the mantle with a mass of cement, a die to form a screw threaded passage in the mass of cement, and a slap hammer connectable to the pulling elements. This method of removal requires direct attachment by screw thread to a portion of the remaining mantle of cement or attachment of a threaded pulling element by fresh methylmethacrylate cement, which is said to soften the old mantle of cement. Such softening prevents bond creation between the old cement mantle and the freshly applied methylmethacrylate preventing any removal of the old cement mantle. Moreover, methylmethacrylate is a brittle resin and will readily fracture upon being subjected to tensile pull by slap hammer.
U.S. Pat. No. 5,064,426 to Huebsch discloses an apparatus for removal of bone cement. Bone cement is removed from a bone cavity, such as the intramedullary canal, during a prosthetic revision. The bone cement is pre-molded by a thermal chisel, which includes a shaft for extending into the bone cavity, a plasticizer chisel on a working end of the shaft, and a heat element carried by the shaft for heating the chisel to a temperature within a range of temperatures sufficient to plasticize the bone cement. This deforms and weakens the bone cement upon direct non-impact type contact between the heated tip of the chisel and the cement. The cement is removed by pre-molding it with the heated working end of the thermal chisel, preferably by molding a distally located circumferential furrow in the bone cement and then molding circumferentially spaced apart longitudinal furrows from the circumferential groove to the proximal end of the bone cement. Upon rehardening of the bone cement, these thermally molded furrows form weakened areas within the bone cement so that the regions of bone cement between the weakened areas can be removed by an impact type chisel. Use of this heated tip raises the temperature of the cement sufficiently to melt or soften the cement. The bone tissue that is in direct contact with the cement also reaches the same softening or melting temperature, which is a fixed temperature according to the composition of the cement used. Exposure of the bone tissue to such high temperatures compromises the ability of the bone tissue to heal and bond to a new implanted femoral prosthesis.
U.S. Pat. No. 5,152,792 to Watkins et al. discloses an apparatus and method for gauging and controlling process steps used to remove prosthetic joints. Over tightening of the threaded rods used to engage and remove the cement for prosthetic joints is avoided by measuring the depth of the passages into which the rods are threaded. Sleeves on the rods are provided to serve as visual indicia of the extent of penetration of the rods into the cement. A depth gauge is calibrated in both units of length and screw thread turns, for the measuring function. The sleeves are slidably received on the rods and proportioned to engage the edges of the passages into which the rods are threaded. In use, the sleeves slide toward a marker as the rods are threaded into place. Sequentially sized tools are screwed into the mass of cement injected into the bone cement mantle and torsional and pulling force is applied to extract the bone cement mantle. Insertion and hardening of the cement into the bone cement mantle takes time, and the fluid cement injected is said to soften or partially dissolve the bone cement mantle. As a result, the bond between the poured cement and the bone cement mantle is weak and the application of torsional and pulling forces may separate at this interface between the injected cement and the bone mantle cement, resulting in incomplete or poor extraction of the bone cement mantle.
U.S. Pat. No. 5,167,619 to Wuchinich discloses an apparatus and method for removal of cement from bone cavities. This surgical apparatus has a hand piece with a vibration source for generating mechanical vibrations in response to current supplied to the vibrator. A elongated hollow tool is attached to the vibration source of the hand piece. The tool extends away from the hand piece to the cement to be removed. Cement is removed using the surgical apparatus by applying the tool to the cement and thereby applying mechanical vibration to the cement, causing the cement to melt. Removal of cement is accomplished by suction through the hollow elongated tool. In an alternate method, the tool is rotated to apply shear forces to the cement being removed. The tool is then cooled, used to damp lateral vibrations at the tool end. The cement is irrigated, while being melted and removed. In this arrangement, the vibratory and rotary motion of the tool creates sufficient friction generated heat to melt the bone cement mantle, causing molten cement to be drawn through the central aperture of the hollow tube. Since the bone cement mantle is in intimate contact with the bone tissue, such heat generation exposes the bone tissue to heat, preventing its ability to heal and bond to a new implant.
U.S. Pat. No. 5,190,551 to Chin et al. discloses a controlled apparatus and method for extracting cement mantles from bone recesses. A cement plug, received within a bone recess, is extracted by forming a bore within the plug, tapping the bore to form internal screw threads therein, engaging the threads with a pulling tool, and applying tension to the tool to extract the plug. The method for removing a cement mantle includes steps of: (i) filling the bone cavity with a fluid cement; (ii) inserting an elongate curvilinear rod in the fluid cement; (iii) curing the fluid cement, rod, and mantle to form a unitary mass; (iv) withdrawing the curvilinear rod from the mass; (v) tapping to form a screw-threaded section therein; (vi) engaging the screw-threaded section of the bore with a pulling tool; and (vii) imparting pulling force to the pulling tool to remove that portion of the mass within which the tool is thread-ably engaged from the recess. The curing of the fluid cement takes time, which is not generally available in a surgical situation. For this technique to work, the fluid cement must form an intimate bond with the bone cement mantle. Otherwise, the pulled rod, together with the hardened fluid cement, extracts without pulling the bone cement mantle from the bone cavity.
U.S. Pat. No. 5,222,957 to McColl et al. discloses a method and apparatus for extracting a cement mantle from a bone recess. This method and apparatus effects removal of a pre-placed prosthetic appliance, anchored in place in a bone recess by a cement mantle, and conditions the recess for receipt of a replacement appliance. The preplaced appliance is first pulled from the mantle of hardened cement, holding it within the recess, thus leaving a cavity within the mantle. A screw threaded post having nuts threadably engaged therewith at longitudinally spaced locations is then anchored within the cavity with a new mass of cement. Thereafter, the post is threadably disengaged from the nuts, leaving the nuts in place within the new mass of cement. A pulling tool is then successively engaged with the nuts and tensioned to incrementally remove the mantle from the recess. The hardening of the new mass cement within bone cement mantle requires time, which is not generally available during surgical procedure. In order to harden a new mass of cement incrementally in one-half inch increments, the bone cement mantle must intimately bond with the old bone cement mantle, and the hardened new mass of cement must fracture at specified incremental locations. In practice, these features may not readily occur, leaving portions of the bone cement mantle within the bone cavity.
U.S. Pat. No. 5,413,578 to Zahedi discloses a device for removing a bone cement tube. This device for removing a bone cement tube in a bone cavity after the removal of the endoprosthesis comprises an ultrasonic generator with an essentially cylindrical guide section, the free end of which carries the sonotrode, which emits the ultrasound. The diameter of the guide section is less than the internal diameter of the bone cement tube, and its length is adapted to the length of the prosthesis shaft or to the length of the bone cement tube. It has been found that a layer of cement, which covers a bone substance, loosens when it is ultrasonically radiated with a frequency in the region of 40 kHz. This cement layer can be removed from the surface of the bone as a complete block of cement. The substance of the bone is not weakened due to this procedure. Since the ultrasonic frequency is emitted by the sonotube, an ultrasonic coupling agent must be disposed between the sonotube and the bone cement tube in order to couple the ultrasonic frequency energy. No such coupling agent is indicated, with the result that energy transfer to the bone cement tube will be inefficient.
U.S. Pat. No. 5,470,336 to Ling et al. discloses a system for performing hip prosthesis revision surgery. This hip prosthesis revision surgery apparatus includes means for preparation of the cavity left after removal of the original prosthesis. The old bone cement tube or mantle is completely removed first by drilling and by progressively increased sizes of reamers. The old restrictor at the bottom of the bone cavity is also removed. The reamed bone cavity is larger in size than that needed for the new implant, and is shaped to proper size by tamping cancellous bone graft material. Following removal of the old prosthesis, old cement and old restrictor, a new cement restrictor or plug is placed at or near the bottom of the cavity in femur. A guide-wire, having external threads, is threadedly engaged with the new restrictor. A tamp having a stem portion and a longitudinal passageway is inserted into the cavity. The tamp is positioned to be driven into the cavity by means of the rasp handle, which is impacted by a hammer or other impacting device as it is driven to the desired position within the cavity to crush the cancellous bone graft to a desired density. Following tamping of the cancellous bone graft material to the desired density and the resultant formation of a cavity having the proper size and shape, the tamp may be removed from the newly formed cavity. The rasp handle is then removed and the guide-wire may be unscrewed and removed from the restrictor. The new cavity is now ready to receive the new prosthesis. The '336 patent disclosure deals with packing a larger sized bone cavity with graft material. It does not address removal of old bone cement mantle that is present when a damaged or worn out femoral implant is removed.
U.S. Pat. No. 5,649,930 to Kertzner discloses an orthopedic centering tool. This centering tool is guides a surgical drill bit through the center of a target obstruction within a bone. An adjustable frame of the centering tool includes a pair of right angle sections mounted in a mirror image relationship. The sections are adjustably clamped to one another and, in turn, secure a vertical sleeve for guiding a surgical drill bit and a horizontal sleeve for accommodating an anchor pin within a coplanar arrangement. Various clamps associated with the frame elements and the sleeves permit a surgeon to adjust the tool so that the drill bit is guided through the vertical sleeve to the approximate center of the bone immediately below the obstruction, while the pin anchors the frame to the bone. The surgical frame is attached to the femoral bone in one location only and the frame is therefore rotatable around this femoral bone attachment point, especially when drilling loads are applied to the vertical sleeve. Any such rotation will lead to meandering of the drill bit within the bone cavity that is being drilled to remove bone cement mantle, causing permanent damage to the bone tissue.
U.S. Pat. No. 6,190,392 to Vandewalle et al. discloses a method and apparatus for ultrasonic removal of bone cement material. Ultrasonic removal of bone cement material is accomplished using an auger tool and an ultrasonic transducer/hand piece. The auger tool includes a spiral helical flute, which extends about a cylindrical body. A quick connect mechanism couples the auger tool to the ultrasonic transducer/hand piece. Upon energizing the hand piece, bone cement is heated to a flowing mass so that the flowing mass of bone cement may flow about the cylindrical body and be guided via the spiral helical flute. Removal of bone cement material is accomplished easily and quickly during a revision type orthopedic surgical procedure. The auger tool is vibrated with sufficient ultrasonic power to cause the bone cement to melt, and the molten cement is guided along the helical flute path. The bone tissue directly below the molten bone cement mantle reaches the melting point of the bone cement. Consequently, the heating temperature employed by the method and apparatus of the '392 patent is oftentimes sufficient to damage bone tissue.
U.S. Pat. No. 6,270,502 to Stulberg discloses methods and instruments for performing radial impacting. This radial impacting technique involves using a set of progressively larger radial impactors to pack a medullary canal in a radial direction toward the cortex. For revision cases, graft material, which may be either synthetic or bone graft material, is added into the medullary canal after the previously installed implant has been removed. Packing the medullary canal in the radial direction, as opposed to the conventional approach of packing in a distal direction, is said to provide superior results. The radial impactors are preferably cannulated and may also have holes to assist in the removal of fluids from within the medullary canal. The profile impactors may be either cannulated or non-cannulated and prepare the medullary canal for receipt of the implant. The '502 patent disclosure deals with packing a bone cavity with graft material. It does not disclose or suggest removing old bone cement mantle that is present when a damaged or worn out femoral implant is removed.
“Controlled Perforation: A Safe Method of Cement Removal from the Femoral Canal”, Sydney et al., Clin. Orthop. Relat. Res., 253, April 1990, pp 168-172 discloses a method for removal of cement from a femoral canal. This method involves removal of cement from the canal by way of placing multiple 9-mm perforations at least 5 cm apart on the anterior surface of the femoral shaft. According to the disclosure, the tip of the revision stem should be at least 5 cm distal to the most distal perforation. From January 1984 to December 1986, there were 219 cases of revision total hip arthroplasties performed using this technique. The incidence of ipsilateral postoperative femoral fractures was nine out of 219. Eight of these fractures were at the tip or distal to the femoral prosthesis and were associated with trauma. One fracture occurred through a perforation site and had an associated fracture of the femoral component. Accordingly, this method of drilling multiple 9 mm perforations disclosed by the Sydney et al. publication results in an unreliable surgical procedure.
“A Device for Removal of Femoral Distal Cement Plug During Hip Revision Arthroplasty: A High-Powered Drill Equipped with a Centralizer”, Jingushi et al., The Journal of Anthroplasty, Vol. 15, Iss. 2, February 2000, pp 231-233 discloses removal of a femoral cement mantle in hip revision arthroplasty by way of a high-powered drill. The high-powered drill is equipped with a centralizer developed to remove the distal cement plug safely. Using the drill equipped with a centralizer the cement plug is removed well enough to insert a new component without causing perforation during the operation. The bone cement mantle in the bone cavity is not indicated to be removed by the centralizer mounted high powered drill. Only the bottom cement plug is said to be safely removed.
“Segmental Cement Extraction at Revision Total Hip Arthroplasty”, Schurman et al., Clin. Orthop. Relat. Res., 285, December 1992, pp 158-163 discloses a method for segmented cement extraction during revision surgery. This technique permits segmental extraction of bone cement from the femoral canal through the introduction of fresh cement into the old cement mantle and placement of a threaded rod into the wet cement. The threaded rod is held in place while the cement hardens. The thread-forming rod is then removed leaving a threaded channel in the cement. Extraction rods are then screwed 1.5 to 2.5 cm into the threaded channel. A slap hammer, which attaches to the opposite end of the extraction rod, is used to remove 1.5- to 2.5-cm segments of cement. Fifteen cases involving revision of cemented femoral components were analyzed using the ‘Segmental Cement Extraction reference system. Complete cement removal was achieved in 12 cases. The method produced less damage to the femur when compared with conventional methods. In two cases, there was retained cement along the medial wall of the femur and, in one case, the plug could not be extracted using the ‘Segmental Cement Extraction reference's method. This method requires the fresh cement to bond to bone cement mantle. It requires the fresh cement to break at screw insertion depth, and to carry with it a portion of the bone cement mantle. If the bond between the bone cement mantle and the fresh cement is weak, the bone cement mantle is not extracted. If the fresh cement cures to a stronger cement, fracture may occur unpredictably, creating bone cement extraction problems.
There remains a need in the art for a femoral hip stem explant system that reliably and safely removes any remaining bone cement mantle and bottom plug without damaging the bone tissue due to poor drill or reamer placement or subjecting the bone tissue to excessive heat. Also needed is a femoral hip stem explant system that removes all residue of the bone cement within a reasonable time period, so that the operating time is not excessively prolonged.